1. Field of the Invention
The present invention relates to a method for aging process in a plasma display panel, and particularly, to a method for aging process in a plasma display panel which is able to determine an end point of aging process precisely.
2. Description of the Background Art
As information processing systems are developed and distributed, importance of display device as a means for transmitting visual information is being emphasized. A cathode-ray tube (CRT), which is a main kind of the display device, has disadvantages such as a large size, high operational voltage, and generation of distortion. Recently, flat panel display devices such as liquid crystal display (LCD), field emission display (FED), and plasma display panel (PDP) which are able to improve disadvantages of the CRT are developed. In the PDP among those flat panel display devices, ultraviolet ray of 147 nm wavelength generated when inert mixed gas including He and Xe, or Ne and Xe emits a phosphor, and thereby an image is displayed on a panel. The above PDP can be easily made to be thin film, can be over sized, and has a simple structure, therefore, it is easy to fabricate the PDP and the PDP has higher brightness and luminous efficiency. Especially, in a surface discharge AC type PDP, wall charge is accumulated on a surface of an electrode when the inert gas is discharged, and the electrodes are protected from sputtering generated by the discharge, and therefore, the PDP can be driven with a low voltage and has a long life span.
FIG. 1 is a block diagram showing a 3-electrodes surface discharge AC type PDP according to the conventional art. As shown therein, the surface discharge AC type PDP comprises: a lower substrate 107; an upper substrate 101; a barrier rib 104 for separating the lower substrate 107 and the upper substrate 101 parallelly; fluorescent layers 105R, 105G, and 105B formed on surfaces of the barrier ribs 104 and the lower substrate 107 for generating visible lights of red, green, and blue colors by being excited by ultraviolet ray; address electrodes 106A, 106B, . . . 106N formed on the lower substrate 107 for discharging selectively among a plurality of discharging areas; discharge sustain electrodes 108A, 108B, . . . , 108N installed on the upper substrate 101 for discharging with the address electrodes 106A, 106B, . . . , 106N in the discharging area; a passivation layer 103 for preventing damage of dielectric layer, which will be described later, caused by the sputtering generated in plasma discharging and for raising emission efficiency of secondary electrons; and a dielectric layer 102 for restricting the plasma discharge current and accumulating the wall charges during plasma discharging.
The structure of the surface discharge AC type PDP constructed as above will be described in detail as follows.
The upper substrate 101 and the lower substrate 107 are separated from each other parallelly making the barrier rib 104 therebetween, and the mixed gas such as Ne+Xe, He+Xe, and He+Ne+Xe is injected into the discharging area defined by the upper substrate 101, the lower substrate 107, and the barrier rib 104.
The discharge sustain electrodes 108A, 108B, . . . , 108N are constructed as a pair in every plasma discharging channel, and one (108A) of the pair makes counter discharge with the address electrode as responding to scan pulse supplied during address period, and after that, is used as a scan/sustain electrode making a surface discharge with the adjacent discharge sustain electrode 108B as corresponding to sustain pulse supplied in sustain period. Also, another discharge sustain electrode 108B making a pair with the scan/sustain electrode is used as a common sustain electrode for supplying sustain pulse.
The dielectric layer 102 and the passivation layer 103 are laminated on the upper substrate 101 on which the discharge sustain electrodes 108A, 108B, . . . , 108N are formed. The dielectric layer 102 restricts the plasma discharge current, and accumulates the wall charge during the plasma discharging. The passivation layer 103 generally consists of MgO for preventing the damage of dielectric layer caused by the sputtering generated during plasma discharging and for increasing the emission efficiency of the secondary electron.
The barrier ribs 104 for dividing the discharging areas are stretched vertically on the lower substrate 107, and the fluorescent layers 105R, 105G, and 105B for emitting visible lights of red, green, and blue (R, G, B) by being excited by the ultraviolet ray are formed on surfaces of the barrier ribs 104 and of the lower substrate 107.
Fabrication processes of the PDP constructed as above will be described in brief as follows.
The upper substrate 101 and the lower substrate 107 of the PDP are fabricated, and a sealant is applied between the upper substrate 101 and the lower substrate 107. After that, the sealant is baked at high temperature to attach the upper substrate 101 and the lower substrate 107. In addition, in the exhaust/discharge gas injection process, an air exhaust hole (not shown) is connected on the lower substrate 107, and an exhaust pipe (not shown) is connected to the air exhaust hole to maintain a pressure of the discharging area between the upper/lower substrates 101 and 107 to be 10−6 Torr, after that, the inert gas consisting of Ne, Xe, He, etc. is injected into the discharging area. When the injection of inert gas is completed, the exhaust pipe is tipped-off. At that time, since an end portion of the exhaust pipe is tipped-off if it is heated higher than 800° C., the air exhaust hole on the lower substrate 107 which is opened due to the tip-off is sealed, and the PDP fabrication processes are completed. The PDP fabricated through the above processes has compound layer structure consisting of a thin film layer, a thick film layer, and a gas layer. However, since the discharging conditions are not even in every layers and cells, aging process is performed for a long time for entirely stable discharge.
FIG. 2 is a view showing an aging system of the PDP according to the conventional art roughly. As shown therein, the aging system comprises; an upper substrate 203 and a lower substrate 202; conductive pads 201 and 204 for connecting electrically the upper substrate 203 and the lower substrate 202; and a power supplying unit 205 for supplying electric power to the conductive pads 201 and 204.
The aging process using the above aging system will be described as follows. Left discharge sustain electrodes 108B, . . . , 108N of the upper substrate 203 are all short circuited using the conductive pad 201 under the room temperature (20˜25° C.), and the right discharge sustain electrodes 108A and 108M of the upper substrate 203 are all short circuited using the conductive pad 204. Then, the power supplying unit 205 is connected to both pads to supply the electric power, and thereby discharging is made. Herein, the discharging conditions in aging process are controlled according to the supplied amount of charges by the conductive pads 201 and 204, that is, according to electric power, and therefore, the conditions can be controlled by the voltage and current supplied to the conductive pads 201 and 204.
However, the aging processing method according to the conventional art does not have certain bases which are able to determine the aging end time. Various factors such as voltage, brightness, color temperature, etc. are used as the bases for deciding the aging end time so far. However, the above factors can not determine the aging end time precisely. And this will be described in detail as follows.
FIG. 3 is a graph showing properties of brightness, discharge voltage, and color temperature according to the lapse of time when the aging process is performed according to the conventional art. As shown therein, there is no obvious reference for deciding the aging end time among those the discharge voltage, brightness, the color temperature, etc..
Generally, since the voltage has less sensitivity than that of the electric current, there is a limit to determine the point when the discharge characteristics for thin films having thousands of Å thickness can be stabled. That is, since the discharge voltage of the PDP has a tendency to be saturated easily, and therefore if the aging is ended after deciding wrongly that the discharge voltage is stabled before the PDP is stabled actually, the discharge characteristics are not even when the panel is operated, and thereby a wrong discharge may be generated.
Also, since the brightness or the color temperature among above factors is secondary decision factor which can be known after the visible lights are generated, it is difficult to determine the aging ending time precisely. In addition, even if the aging ending time is determined by the brightness or the color temperature, the aging time is increased excessively, and therefore, the phosphor may be deteriorated and a processing tack-time is increased.
Also, the aging time can be varied according to the status of the phosphor or variables in process, and therefore, the aging time can be determined precisely.